1. Field of Invention
The present invention relates generally to a system and method for planarization of a workpiece such as a semiconductor substrate or wafer.
2. Background of Invention
In semiconductor wafer processing, the use of chemical mechanical planarization, or CMP, has gained favor due to the enhanced ability to increase device density on a semiconductor workpiece, or substrate, such as a wafer. As the demand for planarization of layers formed on wafers in semiconductor fabrication increases, the requirement for greater system (i.e., tool) throughput with less wafer damage and enhanced wafer planarization has also increased.
Two CMP systems that address these issues are described in U.S. Pat. No. 5,804,507, issued Sep. 8, 1998 to Perlov et al. and in U.S. Pat. No. 5,738,574, issued Apr. 15, 1998 to Tolles et al., both of which are hereby incorporated by reference in their entirety. Perlov et al. and Tolles et al. disclose a CMP system having a planarization apparatus that is supplied wafers from cassettes located in an adjacent liquid filled bath. A transfer mechanism, or robot, facilitates the transfer of the wafers from the bath to a transfer station. From the transfer station, the wafers are loaded to one of four processing heads mounted to a carousel. The carousel moves the processing heads and wafers to various planarization stations where the wafers are planarized by moving the wafer relative to a polishing pad in the presence of a slurry or other fluid medium. The polishing pad may include an abrasive surface. Additionally, the slurry may contain both chemicals and abrasives that aid in the removal of material from the wafer. After completion of the planarization process, the wafer is returned back through the transfer station to the proper cassette located in the bath.
Another system is disclosed in U.S. Pat. No. 5,908,530, issued Jun. 1, 1999 to Hoshizaki et al., which is hereby incorporated by reference in its entirety. Hoshizaki et al. teaches an apparatus for planarizing wafers wherein the wafer is subjected to uniform velocity across the wafer surface with respect to the abrasive surface. The uniform velocity across the wafer surface coupled with a multi-programmable planarization pattern results in a uniform rate of material removal from the wafer surface. In addition, Hoshizaki et al. provides a number of optional routines that allow a user to fine tune material removal from the wafer.
Another system is disclosed in U.S. patent application No. 09/556,495, filed Apr. 21, 2000 to Sommer (hereinafter referred to as Sommer xe2x80x2495 describes a planarization system comprising two polishing heads for retaining wafers coupled to a drive system disposed over a single web. By polishing two wafers simultaneously on a single web, the rate of wafer throughput is enhanced.
The systems described above can generally utilize polishing pads with and without abrasive finishes. The polishing pads may be stationary or move relative to the wafer, e.g., rotationally or linearly. Additionally, abrasive slurry, de-ionized water and other fluids may be delivered to the polishing pad during processing.
Common to these and other systems is the need to reduce the cost of ownership and to increase the wafer throughput. Both of these attributes are highly desirably and necessary to remain competitive in the semiconductor marketplace. The cost of ownership can be effectively reduced by providing a system having a compact footprint. Small system footprints allow for a greater number of systems in a facility production area, thus decreasing the system cost per unit factory area while contributing to an increase in factory capacity by freeing floor space for other processing and support systems. Additionally, increased throughput both contributes to reducing the cost of ownership while reducing manufacturing costs associated with production/machine time. Increased throughput also decreases the cost per processed wafer that allows for greater profitability and increased latitude on product pricing, factors that greatly enhance the manufacturer""s market position relative to his competitors.
Therefore, there is a need for a chemical mechanical wafer planarization system that provides increased wafer throughput while minimizing the footprint of the system.
One aspect of the present invention provides a chemical mechanical planarization system for planarizing wafers including a wafer transfer corridor. In an exemplary embodiment, the system includes a transfer corridor, at least one corridor robot, one or more polishing modules and at least one loading device. The corridor robot is disposed in the transfer corridor and is positionable between a first end and a second end of the transfer corridor. The one or more polishing modules each include one or more polishing heads for holding workpieces during processing. The polishing modules are disposed adjacent the transfer corridor. The loading device is disposed between the transfer corridor and the polishing modules and is adapted to transfer workpieces therebetween. Generally, the loading device includes at least one load cup.
In another embodiment of the invention, the planarization system additionally comprises a first robot, a second robot, one or more workpiece (e.g., wafer) storage cassettes, and a cleaning module. The first robot is adapted to transfer the workpiece between the storage cassettes, the cleaning module and the first staging area. The second robot is adapted to transfer the workpiece between the second staging area and the cleaning module.
In another aspect of the invention, a method of processing a workpiece is disclosed. In an exemplary embodiment, the method generally comprises the steps of gripping one or more workpieces from a first staging area by a first robot, transferring the one or more workpieces gripped by the first robot to one or more load cups, transferring the one or more workpieces in the load cups into respective polishing heads of a first chemical mechanical polishing module, processing the one or more workpieces, transferring the one or more workpieces from the respective polishing heads into the one or more load cups, gripping one or more workpieces from the one or more load cups by the first robot, and, transferring the one or more workpieces gripped by the first robot to a second staging area. In another embodiment, the method additionally comprises the steps of simultaneously processing a second set of one or more workpieces in a second polishing module in a loading sequence similar to the first.